The purpose of the project is to study the effects of head and body tilt on the orientation specificity, orientation range, other receptive field characteristics and discharge behavior of single visual neurons of the geniculate body and primary visual cortex of anesthetized and unanesthetized cats. Initial efforts will be directed to quantitative definition of the orientation selectivity and orientation range in simple-field and complex-field neurones of visual cortex. Effects of head and body tilt on single cells of the lateral geniculate and visual cortex recorded acutely and in chronic microelectrode studies will be undertaken. The effects of acute and chronic interruption of vestibular afferent information to the visual system by section of the VIII nerve will be studied.